In‐Situ X‐ray Diffraction as a Tool to Probe Mechanical Phenomena Down to the Nano‐Scale

Abstract

X-ray diffraction (XRD) represents a classical technique of materials science providing quantitative data on the structural properties of crystalline materials. [1] Synchrotron light with high brilliance, tuneable energy and selectable beam size has dramatically improved the experimental possibilities and opened the path for novel XRD experiments in the past two decades. [2] XRD beamlines with dedicated infrastructure have made it possible to significantly increase the spatial resolution of the diffraction experiments, decrease the acquisition time and increase the resolution in the reciprocal space. In recent years, XRD was extensively used to characterize structural properties of materials in-situ whereby external temperature, mechanical load, magnetic or electric fields were applied. [e.g.3±6] Nanocrystalline materials (NM) have been the subject of intensive research during the last decades. [7,8] Those materials consist of single-or multi-phase polycrystals with grain sizes below 100 nm and exhibit unique mechanical, physical and chemical properties based especially on the large volume fraction of planar defects (interfaces and/or grain boundaries). NM can be e.g. extremely hard and brittle and can exhibit superplasticity connected with the rotation phenomena of nanocrystallites. [9±11] Biological materials with complex mechanical performance represent also NM with sophisticated structure-property relationship solutions. [12] The understanding of the mechanical properties of NM is an important step in design of new materials with improved mechanical function. In the last few years, a significant level of work has been devoted to the characterization of intrinsic mechanical properties of artificial and biological NM. From the variety of topics, the following two problems have attracted significant attention:-the dependence of yield stress on the grain size in inorganic submicron and nanocrystalline bulk materials as well as in thin films with the thickness in the submicron range. According to the phenomenological Hall-Petch relationship, the yield stress of those materials increases with decreasing grain size. [13,14] In thin metallic films on substrates, very high flow stresses of several hundred MPa were reported, [15] while for some hard coatings values approaching the theoretical strength were found. [16] These results were explained by the specific confinement for the formation and motion of dislocations. The exact physical reasons for the mechanical size effects in NM are, however, not yet fully understood. ± biological tissues like bone, collagen and lignocellulosics exhibit a recovery of the mechanical function or even strain hardening upon cyclic deformation in the plastic region, an effect which was attributed to the presence of so-called sacrificial bonds in collagen or to the Velcro-like bonds in wood. [4,12] It is believed that those phenomena can be related to the specific internal morphology of biological materials possessing an enormous concentration of interfaces which act as slip planes i...

Advanced material characterization techniques for sodium‐ion battery

“…Compared with traditional non-in situ XRD, in situ XRD obtains real-time information about the structural changes during the reaction of materials and provides insight into the reaction of materials during the charging and discharging process, making in situ XRD important for how to improve materials. In situ XRD testing can yield a large amount of comparable information in a short period, and since the entire process of in situ testing is performed at the same location on the same material, the information obtained (whether it is crystal packing, peak intensity, or other parameters) is relatively comparable, [50][51][52] all of which are advantages that non-in situ XRD does not have.…”